Wellhead assembly



June 1965 s. D. JOHNSON ETAL 3,

WELLHEAD AS S EMBLY Filed June 20, 1962 2 Sheets-Sheet l 41 69 s 10 T 525 I4 as u [6 i l8 l5 l2 55 FIG. 3

45 INVENTORS:

GLENN o. JOHNSON BRUCE J. WATKINS BY: I

THEIR AGENT June 1965 s. D- JOHNSON ETAL 3,186,483

WELLHEAD ASSEMBLY Filed June 20. 1962 2 Sheets-Sheet 2 GLENN D. JOHNSON BRUCE J. WATKINS and H755 THEIR AGENT Filed June 2% 1962, Ser. No. 203,969 7 Claims. (Cl. 16689) This application is a continuation-in-part of copending application Serial No. 72,168, filed November 28, 1960, now Patent No. 3,168,337.

This invention relates to a wellhead assembly for closing the top of oil and gas wells and pertains more particularly to a wellhead assembly especially adapted to be employed underwater at the top of a well at offshore loca tions for suspending tubing and casing within the well.

A recent development in the oil industry is the drilling and producing of offshore wells wherein the wellhead assembly and production flowlines are positioned below the surface of the water, preferably on or near the ocean floor so as not to be subjected to the major wind and wave forces and to be out of the way of boats that may navigate in that area. Most offshore well drilling operations of this type are conducted from a platform or anchored barge from which the various pieces of equipment, used in or on the well, are lowered through the water from the barge to their position near the ocean floor. When operating at water depths or at locations wherea diver cannot be employed to assemble the equipment on the ocean floor, it is necessary to provide apparatus that may be lowered through the water from a remote station, and then aligned and connected to other pieces of equipment at the ocean floor.

When installing equipment at the top of an underwater well by the method described in copending application, Serial No. 24,558, filed April 25, 1960, now Patent No. 3,099,316, it is preferred that the wellhead assembly be designed so that no fluid flowliues be connected to lateral discharge ports in the wellhead as this would interfere with the use of certain equipment used in installing or United States PatentO removing the wellhead from the top of the well. Wellheads have to be opened or removed at certain times in order to carry out workover operations within the well,

or in order to replace a tubing or casing string therein.

Presently known wellheads all employ at least one laterally directed fiowline which would interfere with certain underwater operations carried out at the wellhead.

It is therefore a primary object of the present invention to provide a wellhead in which the flow from a plurality of pipe strings suspended therein is directed vertically out of the wellhead.

Another object of the present invention is to provide a wellhead for underwater installations which permits a production tree to be stabbed into the top of a wellhead in a fluidtight manner.

A further object of the present invention is to provide a wellhead wherein at least one production tubing string is nested within a casing in' a concentric manner, with flow from the concentrically mounted tubing and casing strings leaving the top of the wellhead through parallelly-ar-. ranged fiowlines that extend vertically fromithe top of the wellhead.

Still another object of the present invention is to provide a wellhead having a housing made up of a plurality of sections seated one on the otherand secured together by substantially horizontally-directed connector elements.

Another object of the present invention is to provide a wellhead assembly for hanging a casing string and a tubing string therein with means for holding down" the tubing and casing string hangers in a' fluidtight manner within the wellhead.

3,185,488 Patented June 1, 1965 Still a further object of the present invention is to provide a multiple-section wellhead having aligning means for aligning one section with respect-to the other.

It is often preferred that a well have two pipe strings in communication between the lower part of a well and the Wellhead. For ease of installation two, concentric tubing strings are employed rather than two parallel tub ing strings. The outmost of two concentric tubing strings may be a casing string. Since it is necessary to control the flow of fluid through the two concentric pipe strings it may be seen that it is necessary to change the two concentric strings to two parallel strings in side-by-side arrangement at some point in the wellhead in order to install flow control valves in the parallel strings or to provide side-branching flow lines therefrom. A wellhead assembly of this type is shown in copending patent application, Serial No. 72,168, filed November 28, 1960.

Underwater wellhead assemblies are generally arranged so that communication may be had by vertical entry into the wellhead through vertical conduits in addition to the normal flow line or lines from the assembly. With two conduits arranged in side-by-side arrangement near the top of the wellhead assembly to permit control of fluid therethrough by valves, a difiicult problem of closing the open upper ends of the two conduits is presented. Open conduits at the top of an underwater well are normally closed by a plug which must be lowered a hundred feet ormore from a vessel on the surface of the ocean and manipulated in a manner so as to bring it in register and stab it into the open conduits. Since it is most difficult to orient a closure plug so that it can be stabbed in a pair of side-by-side open conduit ends at the top of an underwater wellhead, it is an important object of the present invention to provide an arrangement of vertically-extending conduits at the top of an underwater wellhead assembly whereby the conduits may be readily closed by a closure plug which need not be oriented prior to stabbing it into place.

Still another object of the present invention is to pro vide a multi-section wellhead assembly for underwater wells, the sections of the assembly being provided with self-aligning seating surfaces adapted to be readily assembled at ofishore locations even though it is not possible to lower one section exactly in vertical register on another section.

These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein: Y 7

FIGURE 1 is a diagrammatic view of the wellhead of the present invention shown in partial longitudinal cross section;

FIGURE 2 is a schematic view of a closure plug, taken in partial longitudinal cross section, when positioned in the top of the wellhead assembly of FIGURE 1;

FIGURE 3 is an expanded view of the latching element of the closure plug of FIGURE 2 g and FIGURE 4 is a longitudinal view, taken in partial cross section, of a running tool attached to the closure plug of FIGURE 2.

In FIGURE 1 of the drawing, numeral 11 represents a surface casing or conductor pipe which has been installed in a well in the ground and preferably cemented therein in a conventional manner. At the time the surface casing is positioned in place, a wellheador casinghead in accordance with the present invention has been fixedly secured to the top of the surface casing in any suitable manner such as by welding or by threading. In

the particular arrangement of the wellhead shown in the drawing, the Wellhead comprises lower, intermediate and topsections 1 2, 13 and14, respectively, of a housing which forms the wellhead of the present invention. The

lower section 12 of the housing is preferably provided interior wall of the casing hanger 17 is provided with suitable means, for example, a left-hand thread 22 by which the casing hanger 17 could be attached to the lower end of a pipe string (not shown) for lowering this element 17 and its depending casing string 21 into the well from a suitable operational platform positioned above the well.

The lower and intermediate sections of the housing, 12 and 13, respectively, are provided with sloping seating surfaces 23 and 24, respectively, on the outer surfaces near the upper ends thereof which are adapted to seat thereon cooperating sloping self-aligning seating surfaces 25 and 26 formed on the inner surfaces near the lower ends of the intermediate and upper housing sections 13 and 1 respectively. Seal means 27 and 28 are provided between the cooperating seating faces.

Lower locking screws or bolts 31 are horizontally positioned in a threaded manner within the lower end of the intermediate section of housing 13 and arranged to extend through the wall thereof and into cooperating recesses 3-2 formed in the wall of the lower housing section 12 near the top thereof. in a like manner, the top section 14 of the housing is provided with upper lock screws 33 adapted to seat in recesses 34 in the wall of the intermediate'section 13 of housing near the top thereof. If-

desired or necessary, the lock screws 31 and 33 may be provided with fluidtight seals 35 and 36. While it is preferred in accordance with the present invention to employ a wellhead having lower'and intermediate sections of a housing 12 and 13, respectively, it is quite apparent that theintermediate and lower sections 13 and 12 could be formed as a single element in which case the lower locking screws 31 could be eliminated. However, as a safety precaution in underwater wellhead structures, the housing employs lower and intermediate sections 12 and 13 secured together by means of the lower looking screws 31, which are preferably made of an alloy carbon steel or other suitable material so that they can be drilled out in the event that the upper lock screws 33 become wedged or corroded in a manner so that they cannot be withdrawn from their seating position in order to remove the top section '14 of the housing from the wellhead.

' Formed on the inner wall of the casing hanger 17 near the topthereof is a landing surface 37 adapted to receive and seat thereon a tubing hanger 38. The outer surface of the tubing hanger 38 at the lower end thereof is provided with a tapered seating surface 41, preferably provided with seal means 4 2, such for example as any suitable type of packing or O-rings. The tubing hanger. 38 is adapted to be secured at its lower end to .the top of a string'oftubing/i3, for example, by screw threads. The tubing string 43 depending from the tubing hanger 38 is concentrically arranged within the well casing'string 21.

Formed within the tubing'hanger 33 are a pair of concentrically and vertically arranged and inwardly directed spaced sealing surfaces 44 and 45 against which a pair of concentric nipples 4'6 and 47 are adapted to seal. The lower ends of the nipples re and 47 are pro- 7 vided with packing rings 4% and 49 in order to form a fiuidti'ght seal, Preferably, the portions of the tubing hanger at the top of the sealing surfaces 2-4 and45 are tapered as at and 53 to facilitate 'entryof the lower ends of the nipples into the top of the tubinghanger 3 3. .Gneor more fluid flow passageways 54 extendyertically through the tubing hanger 3% in-communication between the. space between the sealing surfaces 44 and i5 and the annulus 55 formed between the outer wall of the tubing 43 and the inner wall of the casing 21.

Formed in the top of the upper bonnet section 14, which forms the closure section of the housing, is a chamber 56. The outer nipple 46 is fixedly secured at its upper end inside the top section 14 of the housing in a manner such that the open top end of the nipple 46 is in open communication with the chamber 56 within the housing. The top section 14 of the housing and the fluid crossover chamber 56 are closed in any suitable manner by a suitable cover plate 57 which may form the lower flange of a production tree which is secured to the top of the well. The production tree may include a pair of flow conduits fill and 61 having valves 62 and 63 located therein, respectively. The flow conduits G ll and 61 are in communication with a pair of side-branching conduits dim and 61a having flow control valves 62a and 63a positioned therein, respectively. The cover plate 5'7 is connected in any suitable manner to the top section 14 of the housing, as by bolts 64 and 64a.

The flow passageway 61 is in communication through chamber 56, annular space 69 and flow passageways 54, with the annular space 55 between the tubing string 43 and the casing string 21. Thus, means are provided for measuring the casing pressure within the well or for extracting or injecting fluid into the annulus 5'5 between the tubing string 43 and the casing string 21. By providing concentric tube and casing strings 43 and 21, respectively, below the wellhead, smaller diameter pipe may be employed than would be needed if two parallel tubing strings were run down the well. the casing string 21 has considerably more strength than a tubing string 43.

The inner nipple 47 is screw-threaded at its upper end or otherwise suitably secured to the cover plate means or flange 57. The lower end of the inner nipple 47 extends downwardly and when seated against the seating surface 45 of the tubing hanger 38 provides straight through fluidtight'communication between the tubing string 43 and the flow passageway of the flow conduit 69 in the production tree on top of the wellhead. To reduce the diameter of the equipment needed in the present wellhead, sealing surfaces 44 and 45 are preferably axially displaced one from the other as illustrated to give a larger, flow passage between. tween the top and intermediate sections and'between the intermediate and lower sections of the housing, respectivetial groove 77 formed in the outer wall of the tubing hanger 38 so as to hold the tubing hanger in the wellhead and prevent it from being raised off its seat 37 by means of well pressure. Similar lower control screws 80 mounted in holders 81 are provided whereby the screws 8% can be extended to engage a circumferential groove 82 formed-in the outer surface of the casing hanger l7.

Aligning means, as described in copending application, Serial No. 72,168, filed'November 28, 1960, are provided between the various sections of the housing 12, 13 and 14 so that the lock screws 31 and 33 holding the sections togetherare in register with theirirespective recesses 32 and 34' at'the time'the loclcscrewsengage the recesses The recesses 32 and'34 are no larger than the tapered endlof the lock screws31 and 33 so thatan area contact Additionally,

Secondary seals 70 and 71 are provided beassembly is originally lowered into eliminating any plastic flow of metal as would take place in line contact between the two elements.

Fixedly attached to the top of the wellhead assembly of the present invention, as to the valve spool member 85 at the top thereof, is a re-entry housing or lubricator housing mandrel 86 whose lower flange or plate member 87 may be bolted to the valve spool 85, by bolts 88 and 89. The lower end of the lubricator mandrel 86 or the upper end of the valve spool 85 is provided with a crossover chamber 91 in communication between the top of the conduit 61 through the valve spool 85 and a space 91a at least partially surrounding a bushing, member 92 which is screw-threaded into and in communication with the flow conduit 60 in the valve spool 85.

The lubricator mandrel 86 may take a variety of forms but in general the lubricator mandrel 86 is provided with at least one upwardly-extending tubular member 93 having a sealing surface, preferably grooved, as at'94, on the outer wall thereof, against which a surrounding piece of equipment, such as a landing head or a wellhead connector, may be sealed in a fluidtight manner. The lubricator mandrel illustrated is described in greater detailin copending patent application, Serial No. 197,496, filed May 24, 1962, now Patent No. 3,166,124.

In its most simple form the re-entry housing or lubricator mandrel is provided with the upwardly-extending tubular, member 93 which has a sealing surface 95 on the inner wall thereof against which the seals 96 carried by a closure plug 97 may seal in a fluidtight manner. If it is desired to communicate with the separate flow conduits 69 and '61 of the wellhead assembly through the lubricator mandrel 36, it would be necessary to provide a second or inner tubular member 99 as well as the bush- 6. inner wall of the intermediate tubular member 98 near the top thereof against which seals 109 carried outwardly on the closure plug 97 may seal in fluidtight manner. The inner wall of the outer tubular member 93 of the mandel 86 is provided with suitable latching recesses which may be in the form of annular grooves 111 into which the latches 112 and 113 of the closure member may expand.

It will be apparent that since the top of an underwater wellhead assembly is filled with fluid at the time it is desired to insert a closure plug therein, suitable flow passageways must be provided in the plug to allow the escape of fluid trapped in the top of the wellhead through the plug before the plug has been sealed and latched in the wellhead assembly in a fluidtight manner. It is also realized that in order to pull a plug out of the top of a closed wellhead assembly, it is necessary to provide open passageways through the plug across the sealing elements thereof in order to allow fluid to bleed into the top of the wellhead from the surrounding body of water. Otherwise, it would be extremely diflicult to pull a plug out of a wellhead assembly since one would be pulling against a vacuum created beneath the plug when it moved upwardly.

The operating element of the closure plug 97 of FIG- URE 2 comprises a fishing head 114 at the top of an operating rod made up of sections 115 which is screwthreaded to a lower section 116 to which a camming sec- 1 tion 117 is fixedly secured by a rod section 118 whose ing 92. An upward extension of the bushing 92 is formed by the innermost tubular member 99 which is fixedly secured to and depends from the closure plug 97, while being provided with seals 100 which seal against the inner wall 191 of the bushing 92 in a fluidtight manner. Thus, the flow conduit 60 of valve spool member 85 is in communication, through the bore 191 of the bushing 92, with the bore 102 of the innermost tubular member 99. At the same time the flow conduit 61 in the valve spool member 85 is in communication, through the cross-over chamber 91, with the space 104 between the bushing 92 and the lower end of the intermediate tubular member 98, which space becomes the space between the innermost and intermediate tubularmembers 99 and 98, respectively. The tubular members 98 and 99 are in spaced rela tionshipwith each other so that fluid can flow between them. t

For this particular oil installation it is also desired to have a third flow conduit 106 within the mandrel 86 when the plug 97 is removed. Thus, the intermediate tubular member 98 is in spaced relationship within the outermost tubular member 93 of the mandrel providing a flow conduit 196 which communicates at its lower end with a pressure line 107 which in turn is in pressure communication with the valve operators (not shown) on the valves 62 and 63 and flow control valves 62a and 63a of the wellhead assembly, so as to selectively open and close the valves. The valves are preferably arranged so that pressure from the pressure line 107 of the lubri cator mandrel would open valves 62 and 63 of the wellhead, permitting operations to be carried on through vertical conduit 60 and '61 while at the same time closing the flow control valves 62a and 63a. may be provided with latches or grooves 198 to which a running tool could latch when the plug 97 is removed from the mandrel and the upper portion of the wellhead place after well drilling has been completed. l

In addition to the sealing surfaces on the inner surface of tubular member 93 and the sealing surface 191 on the inner surface 'of the bushing 92, the mandrel 86 is provided with an additional sealing surface 1080: on the.

The bushing 92 upper end is screw-threaded to the bottom of rod section 116. A nut 119 is attached to the bottom of rod section 118 to fixedly secure a piston or a sleeve valve 120 thereto. A second sleeve valve 121 is slidably mounted outside the first sleeve valve 120 and arranged in fluidtight contact therewith while the outside of the sec ond sleeve valve 121 is in fluidtight contact with a cylindrical housing member 122. A stop member and closure element 123 is screw-threaded to the lower end of the cylindrical member 122 while a compression spring 124 tends to urge the outer sleeve or piston valve 121 upwardly away from the stop member 123.

p The upper'end of the cylindrical housing member 122 of the closure plug 97 is provided with a chamber 125 containing a compression spring 126 which acts between an end plug 127 and the shoulder 123 of actuating rod section 1 16 to force the operating rod normally downwardly. The lower face 139 of the actuating rodsection 116 is provided with a pair of downwardly and inwardlydirected camming elements 131 and 132 which are adapted to engage cooperating camming surfaces 133 and 134 formed on latching dogs 112 and 113. Thus, it may beseen that a downward pressure of camming elements 131 and 132 against the camming surfaces 133 and 134 will tend to urge the latching dogs 112 and 113 to move laterally outwardly from the cylindrical housing member 1122 of the closure plug 97 and latch in the annular grooves 111 on the inner surface of tubular member 93 near the top thereof. The camming surfaces 133 and 134 are prefer ably at about a 45 angle so that the latching dogs 112 and 113 may be pushed inwardly on downward movement of the closure plug 97 as it enters the top of the lubricator mandrel 86.

As shown in FIGURE 3 of the drawing, the camming section 117 of the operating rod is provided with olfset camming elements 135 and 136 whose sloping faces are adapted to engage cooperating camming faces or surfaces 137 and 138 on latching elements 113 and 112, re spectively. The camming elements 135 and 136 are olfset from each other with the camming element 135 .being nearer the front of the camming section, as viewed and the other camming element 136 being offset to the rear of the element 117. This allows forsimultaneous actuation of both of the latching dogs 112 and 113 by a The closure housing s een-as is provided with an upper shoulder .140 which presses against the bottom of the camming section 117 when the upper screw-threaded end 141 of the rod section 113 is screwed in the recessed portion 142 of the upper rod section 116. A lower shoulder 143 engages the upper end of the innermost piston or sleeve valve 121), as shown in FIGURE 2. The latching dogs 112 and 113 are illustrated as being provided with a series of horizontallydisposed teeth or serrations 144 and 145 on the outwardly-extending surfaces-thereof. It is to be understood that these teeth may be in the form of pins or any other suitable latching device. V

In FIGURE 4 a tubular running tool 147 is shown as being secured to the lower end of a pipe string 148 for running the closure plug 97 into place in the top of a wellhead during running or lowering the closure plug 97 into place. The running tool 147 is seated in a shoulder 149 on the cylindrical housing member 122 of the closure plug 97. The two elements are releasably secured together by means 'of a shear pin 150 which is shown in its sheared position in FIGURE 2 as portions 150 and 150a.

At the time the closure plug 97 is secured in the running tool 147 the head 151 of an adjustable screw 152 'bears against the top of an auxiliary operating rod or a valve rod 153 to hold it in its most downwardlyposition. The valve rod 153 (FIGURE 2) extends through the fishing head 114 and the operating rod sections 115, 116, 117 and 118 and is slidably movable therein. The lower end of the rod 153 bears against the closed lower end 154 of the outer sleeve valve 121 and the action of the compression spring 124 against the sleeve valve 121 tends'to raise the valve rod 153 to the position shown in FIGURE 2. At the time the closure plug 97 is'shearpinned to the running tool 147 as shown in FIGURE 4, the closed lower end 154 ofthe outer sleeve valve 121 is in contact with the stop member 123 at the lower end of the housing member 122 of the closure plug 97. The shoulder 155 extending outwardly on the housing member 122 is adapted to engage the top end'of tubular member 93 of the lubricator mandrel 86. An annular seal 156 is provided just below the shoulderv 155 to keep sea Water from entering the top of the lubricator man:

drel. The seal 156 is not designed to keep fluid within the lubricator. mandrel from coming out and thus, any fluid which can escape to the central chamber 157 of the closure plug 97 can escape past the latching dogs 112 and 11-3 and past the seal 156 and out of the lubricator mandrel. Seals 56, 109 and 100, however, are pressure seals which prevent the escape of fluid attliese points.

me-mber 122 may be provided with one or more fluid passageways 158 which permit'the escape of fluid from flow conduits 107 through 1126. and 158into the chamber 157 andthence out of the lubri cator mandrel.

At the time closure plug 97 is shear-pinned to the running tool 147 as shown in FIGURE 4, the valve rod 153 v is depressed so that the outer sleeve 15- touches the stop a 161 and thence through fiowpassageways 162 and 163 to the low pressure chamber 157 from which the fluid can escape in a manner described hereinabove.

At the same time, with the outer sleeve valve 121 1 at its lower positiornthe port 164 through the housingmemher is in communication with flow passageway 163 and g member 98 may escape through conduit 158 into chamber 157 and thence out of the lubrica-tor mandrel. During normal operations, with the underwater wellhead closed by the closure plug, the various elements of the closure plug assume the position illustrated in FIGURE 2.

When it is desired to pull the plug out of the Wellhead, any suitable type of fishing tool may be employed which will engage the fishing head 1 -14 of the plug whereby an upward pulling force can be exerted on the operating rod 1 15. The fishing tool would be mounted on the lower end of a pipe string and would preferably be provided with a series of spring fingers 1 66 and adapted to-be forced outwardly by a camming surf-ace 167 on the top of the fishing head 1114 and subsequently engage the shoulder 168 of the fishing head 1 14; Upon an upward pull of the fishing head 114, the operating rod sections 1 15, 116, 1 17 and 118 as well as the inner sleeve valve 12% move upwardly with it. Before the camming elements 135 and 136 on the camming section 1 17 engaged cooperating camming surfaces 137 and 138 on the latching dogs 1 12 and 113, the upper port 179 through the inner sleeve valve 121) would be in alignment with port 171 through the wall of the outer sleeve valve 121and also in alignment with port 172 through the wall otthe housing member 122 and in communication below pressure seal N9 with the spacebetween tubular members 2' 8 and 99, thus allowing pressure to equalize as port 170 in the inner sleeve valve 121) is in communication through flow passageways 17 3 with the low pressure chamber 157. At the same time the lower port 174 through the inner sleeve valve 121) is in communication with port 175 through the outer sleeve valve 121 and through port 176 through the housing member 122 so as to permit fi-uid to bleed into the chamber 12d Within the innermost tubular member 59. After these ports are opened, continued pulling on the fishing head 114 causes the camming elements 135 and 136 to retract the latching dogs 1 1 2 and 11-3 so that the closure I member 97 can .be pulled out of the wellhead assembly.

thence with chamber 157 whereby any fluid between tubular members his and 99 may escape. Also, at this time any fluid trapped between the tubular member 93 and tubular We claim as our invention: 1. A wellhead assembly for supporting a tubing string concentrically disposed within a casing string, both of said strings extending into a well, said wellhead assembly comprising v l t Y (1) housing means having a firstiiuid cross-over chamher formed therein in communication with a casing string to which the housing means is secured, V

(2) a portion of said housing means having a second fluid cross-over chamber in spaced relation above said first cross-over chamber 1 (3) a portion of said housing means between said crossover chambers having I i (a) a first conduit means in communication with said tubing string suspended within said casing string and extending upwards therefrom, and

(b) second conduit means parallel to and independent of said first conduit means in communication with said first and second cross-over chambers, r

(c) said first conduit means including wall strucjture isolatingthe first conduit means from communication wit-h said chambers and from the secondconduit vmeans, and

(4) at least a pair of flow passageways arranged in concentric spaced relationship at the top of the housing means, the outer flow passageway of said concentric flow passageways being in communication with said second cross-over chamber.

2 The apparatus of claim 1 including plug means adapted to be secured to the upper, end of said assembly for closing the concentric flow passageways therein.

3. The apparatus of claim 1 wherein the housing means includes (c) branching first and second side conduit means in,

communication with'said first and second parallel con- 'duit means, and a a (d) flow control valve means in said first and second side conduit means.

4. The apparatus of claim 1 wherein the housing means includes flow control valve means in said first and second parallel conduit means.

5. A wellhead assembly for supporting a tubing string concentrically disposed Within a casing string, both of said strings extending into a well, said wellhead assembly comprising -'(1) housing means having a first fluid cross-over chamber formed therein in communication with a casing string to which the housing means is secured,

(2) a portion of said housing means above said first cross-over chamber having (a) first conduit means in communication with a tubing string suspended within said casing string and out of communication with said first crossover chamber (in) second conduit means parallel to and independent of said first conduit means and in communication with said first cross-over chamber,

(c) flow control valve means in said first and second parallel conduit means (3) a portion of said housing means having a second fiuid cross-over chamber at the top of said second parallel conduit means and incommunication therewith, said fiow control valve means being positioned between said first and second cross-over chambers,

' (4) at least a pair of concentric pipes in concentric spaced relationship extending upwardly from the top of said housing means and being fixedly secured thereto, the annular space between the pipes being in communication with said second cross-over chamber, and

(5) removable plug means for closing the top of said pair of concentric pipes. V

6. The apparatus of claim 5 including a lubricator mandrel afiixed to the top of said housing and surrounding said pair of concentric pipes in spaced relationship thereto throughout a major portion of the length thereof and forming a flow passage therebetween, said pair of concentric pipes and the surrounding lubricator mandrel hav- (2) a portion of said housing means above said first cross-over chamber having (a) first conduit means in communication with a tubing string suspended within said casing string (b) second conduit means parallel to said first conduit means and in communication at the lower end thereof, with said first cross-over chamber,

(c) branching first and second side conduit means in communication with said first and second parallel conduit means,

(d) flow control valve means in said first and second side conduit means (e) flow control valve means in said first and sec- 0nd parallel conduit means,

(3) a portion of said housing means having a second fluid cross-over chamber at the top of said second parallel conduit means and in communication therewith,

(4) at least a pair of concentric pipes in concentric spaced relationship'extending upwardly from the top of said housing means and being fixedly secured thereto, 7

(5) a lubricator mandrel affixed to the top of said housing means and surrounding said pair of concentric pipes in spaced relationship thereto over a substantial portion of the length thereof and forming a flow passage therebetween,

(6) said pair of concentric pipes and the surrounding lubricator mandrel having axially-displaced sealing surfaces formed thereon, and

(7) removable plug means for engaging said sealing surfaces and closing the top of said pair of concentric pipes and said lubricator mandrel.

References Cited by the Examiner UNITED STATES PATENTS 1,944,573 =l/3'4 Raymond et al 16695 2,085,119 6/37 Penick et a1 16695 2,104,177 1/ 3-8 Yancey 13889- 2,134,200 10/ 38 Pivoto l66--86 2,334,303 ll/43 Allen et al. 138--89 2,335,355 11/43 Penick et al l66-89 X 2,766,830 10/56 Church 166- 88 X 3,062,301 9/62 Watts et a1 166--37 FOREIGN PATENTS 783,396 9/57 Great Britain.

CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN HERSH, Examiner. 

1. A WELLHEAD ASSEMBLY FOR SUPPORTING A TUBING STRING CONCENTRICALLY DISPOSED WITHIN A CASING STRING, BOTH OF SAID STRINGS EXTENDING INTO A WELL, SAID WELLHEAD ASSEMBLY COMPRISING (1) HOUSING MEANS HAVING A FIRST FLUID CROSS-OVER CHAMBER FORMED THEREIN IN COMMUNICATION WITH A CASING STRING TO WHICH THE HOUSING MEANS IS SECURED, (2) A PORTION OF SAID HOUSING MEANS HAVING A SECOND FLUID CROSS-OVER CHAMBER IN SPACED RELATION ABOVE SAID FIRST CROSS-OVER CHAMBER, (3) A PORTION OF SAID HOUSING MEANS BETWEEN SAID CROSSOVER CHAMBERS HAVING (A) A FIRST CONDUIT MEANS IN COMMUNICATION WITH SAID TUBING STRING SUSPENDED WITHIN SAID CASING STRING AND EXTENDING UPWARDS THEREFROM, AND (B) SECOND CONDUIT MEANS PARALLEL TO AND INDEPENDENT OF SAID FIRST CONDUIT MEANS IN COMMUNICATION WITH SAID FIRST AND SECOND CROSS-OVER CHAMBERS, (C) SAID FIRST CONDUIT MEANS INCLUDING WALL STRUCTURE ISOLATING THE FIRST CONDUIT MEANS FROM CONMUNICATION WITH SAID CHAMBERS AND FROM THE SECOND CONDUIT MEANS, AND 